[MATH] dont use a calculator

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jasaiyajin

jasaiyajin

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sqrt(x+8) - sqrt(x-8) = 2


no calc, i want to see it written step by step ^_^

EDIT: sqrt == squareroot

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  • Sep 24, 2005
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sqrt(x+8) - sqrt(x-8) = 2
= 2+sqrt (x-8) = (x+8)
you know that whatever the squareroot of (x+8) is, is 2 bigger than (x-8), so I tried sqrt of 4 on the right side, and sqrt of 16 on the left side, since sqrt of 16 = 2 + sqrt of 4, but that didn't work out. so then I tried sqrt of 9 on the right side, since 9 is the next smallest perfect sq. so 25 on the left side since sqrt of 25 = 2 + sqrt of 9 and it worked. to get 9 on the right side under the sqrt, the you set the equation as x=9+8, x = 17. then on the left side I know my x value = 17, 17 + 8 = 25. sqrt of 25 = 2 + sqrt of 9.

there's probably an easier way to do this, but I'm used to plugging #s

  • Sep 24, 2005
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wow sketch, you are doing better than i did.. lol.. he hav to explain it to be before i got the answer...

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j0n0

j0n0

Increadibly Cute

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The way I was taught to do it is
(sqrt(x+8) - sqrt(x-8))^2 = 2^2 square both sides
x+8 -2sqrt(x^2-64) + x-8 = 4 now simplify and rearrage
x - 2 = sqrt(x^2-64) square both sides again
x^2 - 4x + 4 = x^2 - 64 simplify
4x = 68
x = 17 done

An eye for an eye brings justice, but it is compassion that changes a man.

Another point of view doesn't necessarily make yours more or less right.

  • Sep 25, 2005
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2[sqrt(8)]=2

cause the sqrt(x) and the sqrt(-x) are exact opposite and hance cancel.

Then leaving the sqrt(8) and the sqrt(-8), and b/c the minus a negative, it then adds together instead of subtracting. This leaves it being 2 sqrt(8).

Hence we arrive at our answer, 2[sqrt(8)]=2

j0n0

j0n0

Increadibly Cute

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Sorry Hasaki-Keissi, but that is wrong. 2*sqrt(8) doesn't = 2. Put i2*sqrt(8) in the calculator and you will get 5.656854 and not 2. But if you plug in 17 for the original equation, you will get 2.

An eye for an eye brings justice, but it is compassion that changes a man.

Another point of view doesn't necessarily make yours more or less right.

  • Sep 25, 2005

leosama84

leosama84

::Peace Maker::

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aaah math! i haven't been studying for quite a while...so if u don't practice sumfin, u'd forget it by time ^_^....i would've luved to participate in it though!

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xange

xange

~white bunny~

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hey man
nice way to get your homework freely done
a good one XD

she'll **** you just for the taste


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  • Sep 26, 2005

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